Method and apparatus for conditioning and defibrating a web of paper pulp prior to air laying

ABSTRACT

IN AN APPARATUS FOR A METHOD OF DEFIBRATING A WEB OF WOOD PULP, THE WEB IS CONDITIONED BY A UNIFORM SPRAY OF LIQUID IMPINGING ON THE WEB IN A UNIFORM PATTERN AND WITH A UNIFORM DENSITY ACROSS THE FULL WIDTH OF THE WEB. THE SPRAY MAY BE A MIXTURE OF MINERAL OIL AND WATER AND MAY BE GENERATED BY ROTATING A DIP ROLLER INTO A TANK OF THE LIQUID TO LIFT A FILM OF LIQUID TO A ROTATING BRUSH ROLLER. THE ROTATIONAL SPEED OF THE BRUSH ROLLER IS HELD CONSTANT AND THE ROTATIONAL SPEED OF THE DIP ROLLER IS VARIED   IN ACCORDANCE WITH THE WEB TRAVEL SPEED TO PROVIDE A UNIFORM DENSITY OF SPRAY, PREFERABLY ON BOTH SIDES OF THE WEB. THE LIQUID IN THE TANKS MAY BE HELD AT A CONSTANT LEVEL BY A CONTROLLED SUPPLY MEANS.

y 1971 J. A. MURPHY EI'AL 3,591,450

METHOD AND APPARATUS FOR CONDITIONING AND DEFIBRATING v A WEB OF PAPER PULP PRIOR TO AIR LAYING Filed Aug. 30, 1967 4 Sheets-Sheet 1 July 6, 1971 A MURPHY ETAL 3,591,450

METHOD AND APPARATUS FOR CONDITIONING AND DEEIBRATING A WEB OF PAPER PULP PRIOR TO AIR LAYING Filed Aug. 30, 1967 4 Sheets-Sheet 2 July 6, 1971 MURPHY ETAL 3,591,450

METHOD AND APPARATUS FOR CONDITIONING AND DEFIBRATING A WEB OF PAPER PULP PRIOR TO AIR LAYING Filed Aug. 50, 1967 4 Sheets-Sheet 5 J. A. MURPHY ETAL 3,591, 50 METHOD AND APPARATUS FOR CONDITIONING ANI) UI'JFIBRATTNG I July 6, 1971 A WEB OF PAPER PULP PRIOR TO AIR LAYING 4 Sh ets-Sheer, 4.

Filed Aug. 30, 196'] lllln'lnr a I a lll'llllllln .Illlllll4l1lflll l I United States Patent US. Cl. 162265 Claims ABSTRACT OF THE DISCLOSURE In an apparatus for and a method of defibrating a web of wood pulp, the web is conditioned by a uniform spray of liquid impinging on the Web in a uniform pattern and with a uniform density across the full width of the web. The spray may be a mixture of mineral oil and water and may be generated by rotating a dip roller into a tank of the liquid to lift a film of liquid to a rotating brush roller. The rotational speed of the brush roller is held constant and the rotational speed of the dip roller is varied in accordance with the web travel speed to provide a uni form density of spray, preferably on both sides of the web. The liquid in the tanks may be held at a constant level by a controlled supply means.

This invention relates to the conditioning of stock material and, more particularly, to a method of and apparatus for treating a felted wood pulp web with a conditioning liquid prior to defibrating the Web into a loose fibrous material.

Webs of felted wood pulp are frequently broken into individual fibers or small bundles of fibers and are deposited, by a process known as air laying, to form fibrous pads or batts used in sanitary products such as disposable diapers, sanitary pads, and the like. In such defibrating and air laying processes, it is desirable to produce individual fibers, or as close to this as possible, and to avoid the production of agglomerated clumps or bundles of fibers which will not distribute uniformly in a moving air stream and which may deleteriously aifect the quality of the pad or batt.

During the divelication of the web, the wood fibers tend to become charged electrically and, due to these static electric charges the fibers tend to agglomerate or collect on the walls of the conduits through which the fibers are carried by an air stream. To reduce the buildup of such electrical charges, Wood pulp webs heretofore have been conditioned by running the web through a tank of water. This manner of moistening is not entirely satisfactory as the moisture distribution and density of moisture on the web are not uniformly attained with changes in web speed or with changes in the absorptive characteristics of the webs due to varying manufacturing conditions. Although moisture picked up with this method served to prevent the buildup of static electricity, the moistening did not facilitate the breaking up of the web into individual fibers which would fiow readily in an air stream.

Accordingly, it is the object of the invention to provide an improved method and apparatus for conditioning stock material, such as a wood pulp web, for defibration.

Other objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is an elevational view of a defibrating system embodying the novel method and apparatus of the present invention;

FIG. 2 is a plan view of the system shown in FIG. 1;

FIG. 3 is an enlarged perspective view of a conditioner used in the system of FIG. 1;

Patented July 6, 1971 FIG. 4 is a side elevational view of the opposite side of the conditioner from that shown in FIG. 3;

FIG. 5 is a vertical cross sectional view taken substantially along the line 55 of FIG. 4;

FIG. 6 is a diagrammatic illustration of a liquid supply system for the conditioner of FIG. 3;

FIG. 7 is a vertical cross sectional view taken substantially along the line 7-7 of FIG. 5; and

FIG. 8 is a horizontal, cross sectional view taken along the line 88 of FIG. 7.

In the system illustrated, a shredder 11 and a refiner 13 are provided for defibrating a Web 15 of paper pulp being stripped from a supply roll 17 and fed through a conditioning unit 19. Within the conditioner 19 the web is treated with a liquid to facilitate breaking the Web of felted Wood pulp into individual fibers, or as close thereto.

as possible. From the refiner 13, the fibers are fed into a duct 20 which is supplied with an air stream to carry the fibers to the air laying apparatus (not shown) in which they are formed into a batt or pad.

In accordance with the invention, fine sprays of liquid droplets are applied at relatively high velocity in a uni form pattern across the entire width and on opposite sides of the web Within the conditioner 19. As will be pointed out hereinafter, a liquid spray of water droplets results in more complete defibration into individual fibers, or as close thereto as possible, and also in a relatively trouble free operation of the defibrator, wherein it acts as a coolant and a lubricant. Also, the air laid product may be assured of a predetermined moisture content. When defibrating large quantities of web, for example at a rate of 5-00 pounds per hour, it is important that the refiner be continuously cooled and lubricated. Also, as will be described, a feature of the invention is to provide a substantially uniform amount of liquid droplets on the web, by means of a dip roller 21 (.FIG. 7) rotating 1n tanks 23 to lift the liquid to brush rollers 25 despite varying web travel speeds and diiferent surface conditions of the web.

In practicing the method of the invention, the web 15 is fed along a predetermined path of travel through the conditioner 19; the liquid droplets of a cooling, lubricating and moistening liquid are flicked across the width of the Web; the spray is regulated to provide a substantially uniform distribution of liquid on the traveling web, and then the web is defibrated into loose fibrous material.

In the illustrated embodiment of the invention, the supply roll 17 is disposed on a frame 27 (FIG. 1) supporting the conditioner unit 19. The web 15 is stripped from the bottom of the roll and fed generally horizontally beneath and then upwardly through the conditioner unit to and over a series of vertically and horizontally spaced idler rolls 29 to the top of the shredder 11. The web extends into the nip of a pair of power driven feed rollers 31 provided in the shredder and the feed rollers strip the Web from the supply roll and feed the conditioned web into appropriate cutters (not shown) in the shredder driven by a motor 33 to reduce the Web to small pieces of approximately postage stamp size. The motor and shredder are supported on the upper levels of a main support structure 35. In other forms of defibrating equipment, the web is converted into a fibrous material in a single operation rather than the two step shredding and refining operation described herein; and it is within the purview of the invention that such defibrating equipment be substituted for the shredder 11 and mill 13.

To drive the web feed rollers 31, a drive means is provided which includes a chain 37 trained about a sprocket 39 aifixed to one of the feed rollers 31. The chain extends downwardly at an angle to a sprocket 41 secured to the upper end of a vertical drive shaft 43 which is driven by a remotely located motor (not shown). A chain 45 for driving the conditioner extends from a spocket 47 on the conditioner to a horizontal drive shaft '48 which also drives the vertical drive shaft 43 so that the conditioner unit is driven in timed relationship to the speed of the web travel, for reasons which will be brought out more fully hereinafter.

From the shedder 11, the pieces of wood pulp are carried by an air stream down through a chute 49 (FIG. 1) to the inlet side of the refiner 13 which is supported on a platform 51 beneath the shredder. The refiner 13 may be of conventional construction and may include a pair of closely spaced discs (not shown) which are rotated in opposite directions by a pair of motors 53. The particles received from the shredder are delivered into the space between discs where they are broken and refined into individual fibrs or as close thereto as possible. Friction generates considerable heat in the refiner. To reduce both friction and heat at the refiner which may burn the dry fibers, the water evaporates to a certain extent to cool the refined discs and also acts as a lubricant to reduce the friction. From the refiner 13, the loose fibrous material is deposited nto an air stream moving down through the duct 20 which is connected to a duct 57 which leads to other ducts for mixing and shaping the particles and air streams so as to properly deposit them on a moving web. One manner of air laying the loose fibrous material is shown in copending application Ser. No. 507,089, filed Nov. 10, 1965, now Pat. No. 3,501,813, and assigned to the assignee of this invention, the disclosure of which is hereby incorporated by reference as if fully reproduced herein.

Referring now to apparatus of the conditioner unit 19 in greater detail, its supporting frame 27 (FIG. 3) includes four spaced vertical legs 59, the upper ends of which support horizontally disposed beams 61 disposed parallel to and spaced from each other. Blocks 62 on the beams support a spindle for a first roll, and to change rolls, a second roll may be supported on blocks 64 on the legs 59. Disposed between and extending upwardly from the beams is box-like housing 63 for enclosing the brush and dip rollers. As viewed in FIG. 3, the housing includes a pair of opposite, vertical side walls 65 and 67 joined at right angle corners to front and side walls 69 and 71 which are secured to suitable braces spanning the beams, The top of the housing is covered by a pair of pivotally mounted covers 73 each having an upper horizontal plate and an integrally attached vertical portion extending down and forming part of the front and rear housing walls. These covers are fastened at their lower ends to the housing side Wall by pivot pins 75 and the covers are free to pivot about the pivot pins 75, to the extent limited by chains 77, for the purpose of exposing the interior of the housing when the covers are in open position as shown by the dotted lines in FIG. 7.

Disposed within the walls of the housing 63 are a pair of tanks 23 which are of identical construction and are attached in a similar manner by opposite outwardly extending side flanges 79 abutted against and fastened to the upper sides of an angle brace 81 by nuts and bolts fasteners. Each of the tanks is open at the top and is formed with four opposite side walls 83 extending upwardly from a bottom wall 85 in which is threaded a drain plug 87. The tanks are made relatively deep to serve as a settling tank for foreign matter which may become trapped in the tanks. The inner tank walls are slopped upwardly and inwardly to define therebetween a slot for receiving the web which is to be treated with the liquid.

To guide the web along a straight line path generally centered in the slot and spaced equidistantly from brush rollers 25, the web extends between a lower feed roller 89 and an upper feed roller 91. Each of the rollers is covered with a rubber jacket. The lower roller is journaled on a shaft 93 extending horizontally between opposite housing side walls 69 -and 71. The axis of the lower roller is to the left (FIG. 7) of the path of web travel while the axis of an upper support shaft 95 for the upper roller is to the right of the path of web travel. As the web travels, it moves from the left (FIG. 7) upwardly and is partially wrapped about the lower, inward side of the lower roller 89 and then moves vertically along the vertical center line of the housing to the inner and upper side of the upper roller 91. The web is partially wrapped about the upper roller and travels at an angle to the vertical to exit through a slit 97 in the top of the housing to the idler rolls 29. To hold the web against shifting sideways, edge guides 99 in the form of spaced rings are disposed upon the web rollers 89, 91 and are releasably fastened by set screws at axially spaced locations to engage the web and center it therebetween. These edge guides hold the web centered between the housing side walls 69 and 71 and also centered between brush rollers 25.

To lift a controlled amount of water, dip rollers 21 are supported for rotation about horizontal shafts 101 which are disposed parallel to one another and at the same vertical height within the tanks 23 and the housing 63. The supporting shafts span the housing side Walls 69 and 71 and project through openings in the latter into bearing mounts 103 which are suitably fastened by fasteners 105 to the outer side of the housing side walls. The shaft bearings are protected against water moving axially of the shaft by interior splash guards 107 which are fastened by screws to the interior wall of the housing and extend downwardly and inwardly toward and about the respective ends of the dip roller shafts 101.

In this embodiment of the invention, the dip rollers 21 are formed with an inner steel cylinder fastened to the shaft, and the steel cylinder is rubber jacketed to afford an outer smooth surface for carrying a water film upwardly to the brush rollers 25. The clip rollers are of identical diameter and extend axially beyond the side edges of the web, as shown in FIG. 5, so as to provide water for the entire width of various sizes of webs. Also, the dip rollers 21 are spaced equ'idistantly from the web so that the web receives a uniform density of spray from each dip roller.

The driving means for driving the dip rollers 21 also includes an endless belt 111 (FIG. 4) disposed outside the housing wall 71 and trained about the lower side of a first dip roller sheave 113 and the upper side of a sheave 115 for the other dip roller so that the dip rollers rotate in opposite directions. The sheaves 113 and 115 are fastened on the outer free ends of the respective shafts 101. To keep the belt tensioned, a sheave 117 is carried on a pivotally mounted support bracket 119 fastened to the housing wall in a well-known manner. A drive sheave 121 engages and drives the belt with rotation of the driving chain 45.

With changes in ambient relative humidity or in the moisture content due to a change of pulp rolls, the density of liquid may also be changed to accommodate such variables. To this end, a speed control means is provided by which the increment of speed of operation of dip rollers can be varied or changed relative to the input speed of the driving chain 45. The speed control means is in the form of a conventional speed reducer having gears for stepping down the speed of the input sprocket 47 to drive the sheave 121 at a lower speed. Preferably, the speed reducer is adjustable so that the speed of the dip rollers may be reduced to zero. In operation, the speed of the dip rollers may only be several r.p.m. for warm moist days and conditions and may be as high as 100 r.p.m. for cold, very low humidity days and conditions. To provide a relatively fine and uniform spray of l lquld droplets across the entire width of the web, the brush rollers 25 are, in the specific embodiment of the invention formed with nylon bristles which are ground to form a generally precise outer cylindrical surface in order to maintain a predetermined relationship with the di rollers. Preferably, the bristle ends are slightly spaced from the upper surface of the respective rubber jacketed dip rollers 21. Good results are achieved by disposing the bristle ends spaced from or very slight, minimal contact with the top of each d'ip roller so that the liquid film is removed by the brush rollers 25 and flicked by the ends of the bristles onto the moving web. This is in contrast to having the bristles receive substantial flexing and wiping about an arcuate surface of the dip roller. In this instance, the diameter of each brush roller is five and one-half inches. The bristles are secured to an inner cylindrical roll which has a greater axial length than that of the brushes which have a sufficient axial length to extend beyond the opposite edges of the web. The roll and brushes are fixed to and rotate with their respective supporting shafts 123.

To facilitate alignment of the brush rollers 25 in line contact with the dip rollers 21, the support shafts 123 are mounted for vertical adjustment and extend into and through vertically elongated slots 125 (FIG. 7) in opposite housing side walls 69 and 71. The ends of these shafts are journaled in bearing mounts 127 which are fastened to the exterior of the housing side walls by bolts and nuts 129 slidable in vertically elongated slots 131 in the side walls 69 and 71, on opposite sides and parallel to the slots 125 receiving the supporting shafts. The hearing mounts and the supporting shafts are adjusted in a vertical direction to bring the brushes into a parallel and tangential line contact with the upper rubber surface of the respective dip rollers, and then the nuts are tightened on the bolts to lock the brushes in position. In this position the respective axes of the brush and dip rollers are disposed parallel to each other. The brush rollers are identical in construction and are disposed equidistantly from and on opposite sides of the web 15. Preferably, the respective axes of the brush and dip rollers on each side of the web are disposed in a plane which is, in this instance, both vertical and parallel to the straight line path of the web through the conditioner to assist in providing substantially uniform coating of moisture on both sides of the web. To protect the shaft bearings, splash guards 109 are fastened by screws to the interior side of the housing walls to extend to and about the respective shafts at locations adjacent the housing side walls.

In this instance, a separate driving means is provided to drive the brush rollers 25 at a preselected, constant speed and includes an electric motor 133 (FIG. 3) supported on a bracket 135 fixed to the frame beam 61 for rotating its shaft and an attached sheave 137 about which is trained an endless belt 139. The latter is trained about the upper side of a first sheave 141 fixed to one brush shaft 123 and trained about the under side another sheave 143 fixed to the other brush roller shaft. Therefore, the belt drives the brush rollers in opposite directions of rotation, as shown by the directional arrows in FIG. 7. To maintain a predetermined belt tension, a belt tension pulley 145 is journaled for rotation on a pivotally mounted bracket 147 which is secured to the housing wall"'69 and functions in a well-known manner. The motor runs at substantially constant operating speed. Preferably the speed of the driving means for the brush roller may be preselected to provide a fine and high velocity spray, and good results are obtained when rotating the brushes about 900 rpm. One manner by which the rotational speed may be changed is by using other sizes of pulleys 141 and 143.

To provide a relatively uniform film of liquid on the rotating dip rollers 21 for a given speed of rotation, the liquid level within the tanks is maintained at a predetermined height so that the dip rollers have a uniform portion of their periphery immersed in the liquid. to replenish the water being removed from the tanks, a pair of inlet pipes 145 (FIGS. 6 and 7) extend horizontally across the tanks between and into openings in the side walls 69 and 71 (FIG. 8). A series of holes or ports 146 (FIG. 7) are formed in the bottom of the respective inlet pipes to direct water downwardly into the tank adjacent the upper ends of the sloped tank side walls 83. One end of the inlet pipes is capped, as best seen in FIG. 8, and the other ends are connected to lines 147 (FIGS. 3 and 6), each provided with a shut-off valve 149. The respective lines 147 are joined to a common supply line 151 extending to a pump 153 driven by a motor 155 disposed on the floor beneath the tank. By adjusting the respective valves the amount of inlet fiow to the inlet pipes can be controlled. Excess liquid flowing in the supply line is returned to a box-shaped reservoir or sump 157 through a line 159 extending to the top of the reservoir. A suitable valve 161 is also provided in the line 159.

To drain any excess of liquid in the tanks, overflow ports are provided for the tanks in the form of horizontally disposed pipes 163 (FIGS. 6 and 7) extending into the opposite sides of the tank walls 83. The pipes also serve to drain off floating fibers which may drop from the web into the tanks. The overflow pipes are connected by return lines 165, which extend in a downward and then horizontal loop, to a common return line 167 (FIGS. 3, 4 and 6) emptying into the top of the reservoir 157 as best seen in FIG. 3. Therefore, if the inlet pipes are delivering liquid faster than it is being applied, which would increase the liquid level in the tanks and the amount of immersion of the dip rollers, the overflow lines have sufiicient capacity to drain off the excess and maintain the liquid level constant.

The reservoir 157 is disposed beneath the housing 63 and has a much larger capacity for liquid than the respective tanks within the housing. The reservoir also serves as a settling tank for the overflow liquid and is provided with a filter screen 169 for removing fibers from the liquid passing through the screen. The screen divides the reservoir into two portions, with one portion collecting the fibers and serving as a settling tank for the unfiltered liquid. From the other filtered portion of the reservoir, a supply line 171 extends to the inlet side of the pump 153. Water is supplied to the reservoir through a suitable line 173 which is controlled by a valve 175 operated by a float 177.

A brief description of the operation of the system is given hereinafter to aid in understanding the invention. The wood pulp web 15 travels through the conditioning unit 19 at various speeds and in some instances may stop completely. Webs from different supply rolls may vary in their absorptive characteristics or their initial moisture contents due to the varying. manufacturing conditions under which they were made. Also, the ambient relative humidity may change and necessitate an adjustment in the amount of liquid applied to the web.

As the web travels through the conditioning unit housing 63, it is guided along a substantially straight line path and receives a relatively uniform, high velocity spray of liquid droplets to provide a uniform density of liquid on opposite surfaces and across the full length and along longitudinal length of the web. Thus, the web is not streaked with strips or areas which are more lightly wetted than other areas on the web.

The amount of liquid being applied to the web is adjusted by controlling the speed of the dip roller 21 which rotates at a predetermined reference or base speed to lift a given amount of liquid to the brush rollers. Within limits, an increase in speed of rotation of the dip rollers 21 results in a greater quantity of water being lifted to the brush rollers due to an increased thickness of film on the dip roller and also due to the increased rate at which the dip roller carries the liquid. On the other hand, slowing the rotation of the dip rollers results in less liquid lifted and sprayed by the brush rollers for a given length of web. When the web is stopped, no liquid is lifted to the brush rollers 25 to cause any effective conditioning of the web. In the prior art, the web would become over moistened and even would disintegrate within the dip bath if the web were stopped for a considerable period of time.

It will be appreciated that the air streams carrying the wood pulp fibers through the ducts will dry the fibers considerably and that the relative humidity of the ambient air in these air streams is also an important factor in determining the amount of moisture added to the web prior to the defibrating. In the preferred embodiment of the invention and in accordance with one example, the wood pulp web from the supply roll has an average moisture content of about 8% and, after moistening, .its moisture content is raised to about 13%. In this example, the web is fed at a speed of about 23 feet per minute and provides about 200 pounds per hour of wood pulp fibers. To raise the moisture content to about 13%, approximately 11 pounds per hour of liquid are added to the web as it travels through the conditioner unit. The moisture content after defibrating and air laying is reduced to and held at about 6 /2% moisture content.

The usual range of moisture content after conditioning is about 10%15%. The dip roller speed of rotation is regulated between a few revolutions per minute, when little moisture addition is required, to as high as 100 revolutions per minute when considerable moisture addition to the web is required. During extremely harsh, cold and dry weather, the ambient relative humidity may be quite low and a small amount of mineral oil is added to the water to increase its lubrication qualities. That is, the water itself acts as a lubricant and the oil supplies further lubrication properties. The oil also appears to assist in the breaking up of the fiber bundles into individual fibers. The oil and water are mixed in the ratio of approximately one gallon of oil for 100 gallons of water. An acceptable oil is a light spinning or mineral oil manufactured by Chemtex Products of Rexdale, Canada, and sold under the trade name Clear Lube No. 21.

It has been found that a controlled, uniform application of the liquid to both sides of the web results in a more complete defibration of the wood pulp into individual fibers and avoids large bundles or agglomerations of fibers. The operation of the defibrator is found to be relatively trouble-free as it is cooled and lubricated by the liquid on the web even though relatively high volumes of fibrous material for example, 200 pounds of fibers per hour are being processed. Additionally, the moistening of the individual fibers decreases lumps caused by static electricity and facilitates the flow of fibers to provide an improved air laid product. The problem of scorching fibers due to heat in the refiner has been eliminated. This improved conditioning of the web makes possible the use of the web in difibrators other than the kind illustrated and described herein.

The improved results are thought to be the result of the overall combination of the fine spray applied at a relatively high velocity in a uniform pattern and density across the full width and along the length of the web.

From the foregoing, it will be seen that the web is conditioned in a manner to improve the defibrating process allowing high speed and high volume operations without burning of the fibers. Also, the density of liquid applied I to the web can be closely and uniformly controlled and distributed to obtain a uniformly conditioned web so that the moisture content of the final product may also be controlled.

While a preferred embodiment has been shown on the drawings and described herein, it is not intended to limit the invention by such disclosure but, rather, it is intended to cover all modifications and alternative constructions coming within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A system for conditioning with a liquid and for defibrating a web of wood pulp material to form dry wood pulp fibers having a moisture content within a predetermined range, said system comprising means to defibrate said web into a loose fibrous material, means to feed said web along a predetermined path of travel into said defibrating means, a tank means for holding a supply of liquid, a dip roller having a portion thereof disposed for immersion in the liquid in said tank means and mounted for rotational movement to lift a liquid film thereon above said supply of liquid, a rotatable brush roller having flexible bristles for forming a spray from the liquid film on said dip roller, said brush roller having its axis of rotation extending substantially parallel to said web, and extending transversely across the path of web travel to apply a substantially uniform spray across the full width of the web, and drive means to rotate the brush and dip rollers to impinge the spray on the web with a relatively uniform density across and along the traveling web, said drive means including means to rotate said brush roller at a constant speed, said drive means also including means to rotate said dip roller at a speed which varies proportionally with changes of web speed, said means to rotate said dip roller stopping rotation of said dip roller when said web stops feeding, the amount of liquid conveyed by said dip roller changing with said web speed and terminating with termination of web travel, said liquid evaporating to cool said defibrating means, said liquid acting as a lubricant to reduce friction as said web is defibrated, and said liquid serving to maintain said dry wood pulp fibers within a predetermined range of moisture content.

2. A system in accordance with claim 1 in which another brush roller and another dip roller are disposed at and spaced from a side of said web on a side opposite from said first-mentioned brush roller and dip roller, said web moving along a substantially straight line path between said rollers, the respective axes of rotation of the brush and dip rollers on each side of the web being disposed in planes parallel to the straight line path of the web.

3. The apparatus of claim 2 in which each of said brush rollers has the ends of its bristles disposed to define a cylindrical surface of a generally uniform diameter and in which said brush rollers are mounted to have a substantially tangential line of contact uniformly across the dip rollers whereby a fine uniform spray of liquid droplets is generated.

4. A system in accordance with claim 1 including means for providing and sustaining a predetermined liquid level in said tank means, said dip roller having a predetermined portion thereof immersed in said liquid.

5. An apparatus in accordance with claim 4 in which said means for sustaining the liquid level includes means for supplying liquid to said tank means, overflow ports in said tank means at a desired level whereby excess liquid and floating fibers in said tank means are drained from said tank means, and further includes a recirculating system having a filter for removing said fibers and recirculating said liquid back to said tank means.

References Cited UNITED STATES PATENTS 3,198,199 8/1965 Schultz l34122 2,917,245 12/1959 Polleys 24l-15 2,446,840 8/1948 Leister 1966 2,648,088 8/1953 Bailey 682OOX 2,647,639 8/1953 Grein 210-196X 3,382,140 5/1968 Henderson et al 162-28 S. LEON BASI-IORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X.R. 

